This application is based on and claims priority to Japanese Patent Application No. 11-046,618, filed Feb. 24, 1998, the entire contents of which is hereby expressly incorporated by reference.
1. Field of the Invention
The present invention generally relates to an electrical system for an engine. More particularly, the present invention relates to an improved electrical system that comprises a control unit and a power supply circuit that is connected to the control unit through a time delay switch.
2. Description of Related Art
Recently, engine designers have been emphasizing decreasing emissions, improving fuel economy and, at the same time, maintaining if not improving power output. One way of obtaining at least some of these results involves electrically controlling any of a variety of engine operations. For instance, ignition timing can be altered to better reflect changing engine operating parameters. Moreover, certain characteristics of fuel injected engines can be optimized through an electrically controlled fuel injection system.
An engine control unit (ECU) typically forms a portion of such an electrical control of the engine. For instance, an outboard engine can comprise a number of sensors that sense engine running conditions, ambient conditions or other conditions of the outboard motor that could affect ultimate engine performance. The engine generally includes controllable engine actuators such as, for example, fuel injectors and spark plugs. Signals from the sensors are received by the ECU and the ECU controls the engine actuators in response to the sensed signals. In arrangements in which the engine actuators are the fuel injector and spark plug, for instance, an injection timing, a duration of injection and a firing timing can be controlled and manipulated by the ECU. Thus, the ECU often forms an integral component in an efficiently designed and operated engine. Malfunctions with the ECU, therefore, can impair engine operation.
With reference now to FIG. 1, an exemplary circuit diagram of a prior power supply system is illustrated. It is believed that at least some portions of the illustrated circuit have been used in earlier outboard motor designs. As illustrated, a first portion of the power supply system is located within the watercraft hull while a second portion of the power supply system is located within the outboard motor. The first portion and the second portion can be joined through suitable couplings.
A battery 20 can be provided in the hull of the associated watercraft. In addition, an ECU 22 can be mounted on an engine used in the outboard motor. In the illustrated arrangement, a set of engine actuators, that can include a fuel injector 24, an ignition coil 26 and a fuel pump 28, are connected to the ECU 22. The illustrated power supply system 30 further includes a main switch 32 and a stop switch 34 that is linked with the main switch 32. These switches can be disposed within the hull of the watercraft. A locking relay 36 can be disposed on the outboard motor and a wire harness 38 can extend between and couple a variety of components.
The negative pole of the illustrated battery 20 is grounded and the positive pole thereof is connected directly to the ECU 22 and to the actuators 24, 26, 28 via the relay 36. Preferably, the relay 36 is normally open. The relay 36 generally comprises an excitable coil 44 that holds the contacts 40 in a closed position when supplied with electrical power. One end of the coil 44 can be grounded and the other end can be connected to a relay control terminal 46 of the ECU 22. The positive pole of the battery 20 is also connected to a relay-state detection terminal 48 of the ECU 22 via the main switch 32.
One end of the stop switch 34 can be grounded, while the other end thereof is connected to the ECU 22. The stop switch 34 is normally closed and can be opened when the main switch 32 is closed because the switch 34 is linked to the main switch 32.
When the main switch 32 is closed, the exciting coil 44 is powered through the ECU 22 and the contacts 40 of the relay 36 are closed. Simultaneously, the ECU 22 holds the contacts 40 in this/closed position through a supply of electricity. The engine actuators 24, 26, 28 are, therefore, supplied with power. When the main switch 32 is opened, the stop switch 34 is closed and the ECU 22 stops supplying power to the coil 44. The ECU 22 continues operating for a preset time after the stop switch 34 is closed and then the ECU 22 shuts down.
Because the exciting coil 44 of the relay 36 is controlled by the ECU 22 in the illustrated power supply system 30, the ECU 22 must furnish a separate control circuit for the relay use only. The provision of the seperate control circuit necessarily increases the size and associated cost of the ECU 22. In addition, the ECU 22 is coupled with the sensors and engine actuators through a connector that has multiple terminals. Connectors sold on the market are available for this purpose. However, because such connectors have a fixed number of terminals, for example, twenty four or thirty two terminals, if even one or more terminals, is needed, a special connector must be used. This increases the cost of the ECU 22 and occasionally requires a larger connector size. In this regard, the conventional power supply system 30 needs at least two additional terminals. i.e., the relay control terminal 46 and the relay detective terminal 48, for the activation and deactivation of the relay 36.
A need therefore exists for an improved engine electrical control system that can decrease the required size and cost of the associated ECU.
Accordingly, one aspect of the present invention involve a control system for an internal combustion engine comprising a power source and a control unit controlling an operation of the engine. A coupling switch selectively joins the power source and the control unit. A main switch is provided between the power source and the coupling switch with the main switch being adapted to switch the coupling switch between a coupling condition and a non-coupling condition. The coupling switch is brought to the coupling condition when the main switch is closed. The coupling switch includes an actuator that is coupled to the power source through the main switch with the actuator being adapted to move and maintain the coupling switch in the coupling condition when activated. A delay component is coupled to the actuator with the delay component selectively activating the actuator after the main switch is opened.
Another aspect of the present invention involves a method of controlling a power supply to a controller adapted to control an engine. The method comprising sensing an operational condition of a main switch, generating an output signal when said operational condition of said main switch changes for a preset period of time, and delaying a shutdown of said controller when said output signal ends.
A further aspect of the present invention involves an electrical control system for an internal combustion engine comprising a control unit controlling an operation of the engine and a power source. Coupling means are provided for coupling together the control unit and the power source under a coupling condition. A switch is provided for switching the coupling means between the coupling condition and a non-coupling condition. The coupling means are brought to the coupling condition when the switch is turned on and the coupling means include a self-hold element that holds the coupling means under the coupling condition when activated by electric power supplied through the switch. The control system further comprises preservation means that are provided for preserving the self-hold element under an active condition when the switch is turned off.
For purposes of summarizing the invention and the advantages achieved over the prior art, certain objects and advantages of the invention have been described above. Of course, it is to be understood that not necessarily all such objects or advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein. Moreover, further aspects, features and advantages of this invention will become apparent from the detailed description of the preferred embodiments which follow.